Genetic counseling: Hearing loss - Unknown Cause
Hearing loss - Unknown Cause Introduction *What have you been told about coming to genetics today? *What information have you been given already? *Have you done any research on your own? What have you found out? *What concerns or questions would you like to have answered today? *Outline session Medical History *Complete intake *How was his hearing loss first found? *Eye problems? *Development **Age first walked? Sat up? *EKG? *CT scan *Kidney problems? *Infections? *Neurological problems? Seizures? *Birthmarks? Rashes? Family History *Complete pedigree *Anyone with deafness? Hearing loss? *Eye problems? *White forelock? *Mental retardation? *Kidney problems? Genetics of Hearing loss *1/2000 to 1/1000 children born with profound hearing loss *50% hearing loss has a genetic cause **1/3 related to syndrome **2/3 nonsyndromic **76% recessive genes **20% dominant genes **4% X-linked genes *Hearing loss increases with age **Impact of genetics and environment *Empiric Risks (if no diagnosis can be established) **Hearing parents with one deaf child ***18% risk of deafness in future children **offspring of deaf person and hearing person ***10% risk of deafness **deaf couple without AD hearing loss ***15% risk of deafness in children **child of hearing sib of deaf proband and deaf person ***1/200 risk for deafness Management *Frequent audiologic evaluations to document stability or progression of hearing loss *Determine appropriate habilitation option **Hearing aids **Cochlear implants *Educational intervention Common causes of Genetic hearing loss Syndromic Hearing loss (Accounts for 30% prelingual deafness) *Autosomal Recessive **Usher Syndrome ***Congenital sensorineural hearing loss ***Type 1 *Severe to profound hearing loss *Abnormal vestibular function *Delayed walking and sitting ***Type 2 *mild to severe hearing loss *normal vestibular function ***Type 3 *Progressive hearing loss *Progressive deterioration of vestibular function *Retinitis Pigmentosa *Apparent after first decade of life *Electroretinography can identify abnormalities in photoreceptor function in children as young as 2 - 4 **Pendred Syndrome ***Most common type of AR syndromic hearing loss ***Congenital severe to profound SNHL *Abnormality of bony labyrinth that can be diagnosed with CT scan ***Euthyroid goiter *Develops in puberty to adulthood ***located at 7q22-q13 ***mutations in this gene can also cause nonsyndromic deafness **Jervell and Lange-Nielsen syndrome ***Congenital deafness ***Prolongation of QT wave on ultrasound *Can be detected by EKG *Syncopal episodes can cause sudden death ***Caused by mutations in two different genes *Genetic testing not recommended in evaluation of deaf children *Recommended for those at high risk **Refsum disease ***Severe progressive SNHL ***Retinitis Pigmentosa ***Caused by faulty phytanic acid metabolism ***Can be controlled with dietary modification ***Diagnosed by serum concentration of phytanic acid *Autosomal Dominant **Waardenburg syndrome ***Variable degrees of SNHL ***Pigmentary abnormalities of the skin, hair, and eyes ***Type 1 - lateral displacement of inner canthus (PAX3 gene - clinical testing) ***Type 2 - no displacement of inner canthus (MITF gene - research testing) ***Type 3 - upper limb abnormalities (PAX3 gene - clinical testing) ***Type 4 - Hirschprung disease (EDNRB, EDN3, SOX10 genes - research testing) **Branchiootorenal Syndrome ***Conductive, sensorineural, and mixed hearing loss ***Brachial cleft cysts or fistula ***External ear malformation (prearicular pits) ***Renal anomalies ***20-30% have mutation in EYA1 (locus 8q13) - testing available **Stickler Syndrome ***Progressive SNHL ***Cleft palate ***Spondyloepiphyseal dysplasia causing osteoarthritis ***Genetic causes: *STL1(COL2A1) *STL2 (COL11A2) *STL3 (COL11A1) ***STL1 and STL3 are associated with severe myopia ***Clinical testing available **Neurofibromatosis type II ***Bilateral vestibular schwannomas causing hearing loss *Generally begins in 3rd decade *Hearing loss is generally unilateral and gradual *MRI to diagnose ***Other tumors are associated ***Molecular testing available *X-linked **Alport syndrome ***Progressive sensorineural hearing loss (variable severity) *Generally begins after 10 years of age ***Progressive renal disease ***Ophthalmologic findings ***85% X-linked, AR and AD forms also identified **DFN1 (Xq22) ***Progressive, postlingual hearing loss ***Visual disability ***Dystonia ***Fractures ***Mental retardation *Mitochondrial syndromes Nonsyndromic Hearing Loss (70% hereditary hearing loss) *Autosomal Recessive **50% families DFNB1 **50% other multiple loci ***many different genes - many in only one family *Autosomal Dominant **Many different genes **No one gene causes majority of cases *X-linked **DFN3 (Xq21.1) ***Mixed hearing loss ***Stapedial fixation ***Gene called POU3F4 **Multiple other genes *Mitochondrial **Multiple genes **Low penetrance **Possible environmental factors Psychosocial Issues *Deaf child born to hearing parents *How did you feel when you first found out? *How have your feelings changed? *How have other family members reacted? *Have you been in contact with any other families? *Have you been in contact with any support groups? *What are your biggest concerns at the moment? Resources *American Society for Deaf Children :PO Box 3355 :Gettysburg, PA 17325 :Phone: 800-942-ASDC (parent hotline) :Email: ASDC1@aol.com :Web: www.deafchildren.org *National Association of the Deaf :814 Thayer :Silver Spring, MD 20910 :Phone: 301-587-1788 :Email: NADinfo@nad.org :Web: www.nad.org Notes The information in this outline was last updated in 2002. This material has been imported fom the wikibook "Genetic counseling"[ http://en.wikibooks.org/wiki/Genetic_counseling] under the GNU Free Documentation License.